As well known, gas turbine engines produce useful work by driving a turbine shaft by means of hot gasses obtained by the combustion of compressed natural gas such as air. To improve the overall efficiency of work production, a steam power plant is arranged in combination with the gas turbine plant. In such assembly, the heated gases exiting the turbine flow through an exhaust duct to a heat recovery steam generator (HRSG). The heat from the gases is then utilized in the HRSG to heat water and produce steam, which is in turn used to drive a steam turbine.
Conventional combined-cycle plants as described above are equipped with diverter damper that allows the power plant, comprising the gas turbine plant and the steam power plant, to operate in either a simple-cycle or a combined-cycle mode. To this purpose, a by-pass damper is typically configured to move between a closed or blocking position when operating in a single-cycle mode, where the hot exhaust gas exiting the gas turbine is guided through a by-pass stack part and disposed in the environment, and an open position, operating in a combined-cycle mode, where the hot exhaust gas is admitted in the HRSG and used to produce steam.
In current installations, a diverter damper system for gas turbine applications is usually separated from the gas turbine and the HRSG by an expansion joint positioned at the inlet and outlet of the diverter system. Such known diverting systems are structurally independent from the two major components of gas turbine and steam turbine power plants, interposed there between with a self-sustaining steel structure.
Such systems comprise a first assembly having a blank off plate having upper ends hinged to a supporting structure and movable between a vertical blocking position and a horizontal open position where the exhaust flow is guided versus the HRSG. Downstream the diverting system is located a diffusor component, configured to obtain the critical flow requirements for optimal hot gas temperature distribution and to maximise the efficiency of the heat exchange within the HRSG.
However, such configuration requires the installation of several structurally independent components in series, therefore critically increasing the overall space required for the power plants installation.